Braun tube



Oct. 26,1943. w, UHLMANN 2,332,876

' BRAUN TUBE nFiled March 14, 1939 fnvenfar:

Wolfram 0/71/7701? y mm? Psremea Oct. 26, 1943 BRAUN TUBE WolframUhlmann, Berlin, Germany; the Alien Property Custodian vested inApplicationMarch 14, 1939, Serial No. 261,726 In Germany April 4, 1938This invention relates to new and useful im- 3 Claims.

provements in cathode ray or Braun tubes.

A cathode ray emitted from the electron sun of a cathode ray orBraumtube as employed for metering purposes or in television receiverequipments is subjected to a predetermined deflection along twocoordinates of the coordinate system on its way toward the fluorescentscreen of such tube in order to scan the screen and thus perform imagereproduction on this screen. This cathode ray deflection has heretoforebeen effected by means of homogeneous electrostatic or electromagneticflelds, or even by suitably combining these two possibilities.

My invention consists in specific features of novelty which will bereadily understood from the following description and be pointed out inthe appended claims. reference being had to the accompanying drawing, inwhich Figs. 1 and 2 schematically show alternate aspects of putting thisinvention into effect.

In contradiction to the heretofore known methods of cathode raydeflection mentioned above. that is. the scanning deflection alongcoordinates by electrostatic or electromagnetic fields, it is proposedaccording to the main feature of this invention to effect suchdeflection by means of an electron mirror or mirrors. With an electronmirror, the electric potential i varied to change the effective shape ofthe reflecting surface thereby to change the reflecting angle of themirror. Thus, by impressing a fluctuating potential on the mirror, thecathode ray is caused to scan the screen, such a potential is referredto as a scanning potential. This facility in the first instance involvesthe essential feature that on account of a considerable bend imparted tothe cathode ray when reflected at the electron mirror, also the vesselof the cathode ray tub may be fundamentally changed from its priorstraight form and be accommodated to the bend of the cathode ray, inother words, the vessel ma assume a shap which corresponds to the letterL, or even to the letter V. This is of particular importance when it isdesirable to increase the diameter of the fluorescent screen, since suchincrease would inevitably require a proportional elongation of theheretofore known straight cathode ray tube, while a vacuum vessel of thenew shape as a result of my invention is compact even in connectionwith'a fluorescent screen of larger diameter. Moreover, also the throatportion may cathode ray tubes may be partially or entirely omitted byemploying an electron mirror or mirrors for deflecting the cathode rayto scan and screen With reference to the drawing which illustrates theinvention in a purely schematic manner, G is a V-shaped evacuated vesselof a cathode ray or of a Braun tube according to my invention. Thecathode of this tube is shown at K, while the cathode ray concentrating,accelerating and intensity control means are indicated by dashes, sincethese means form no part of this invention. The-cathode ray T of lumpedcross'sectional area emitted from'the cathode K is projected onto theelectron mirror S. from where it is reflected toward the fluorescentscreen L as shown by either with any predetermined law. My inventionmakes use of the known fact that it is-possible by varying the potentialof the control electrode 2 of the be considerably reduced because of thefact that the electrostatic o'r electromagnetic deflecting means locatedin this portion of the conventional electron mirror S to, graduallychange the reflective action of this mirror from that of a divergentreflector, to that of a convergent or concentrating reflector via thestate of a plane mirror, or vice versa. This effect of reflective actionvariability is involved on account of a change of the electronreflecting equipotential surfaces from con-s vexity via planeness toconcavity, or vice versa, in response to a variable potential applied tothe electrode 2 controlling said equipotential surfaces. The electronreflecting properties of an electron mirror are thus utilized accordingto my invention for reflecting the cathode ray onto the fluorescentscreen L and for gradually defleeting this ray on the screen in eitherdirection along one of the coordinates of the coordinate system, thatis, for the line scanning or for the scanning along the othercoordinate.

The deflection along the other of the coordinates may be achieved in asimilar manner by means of a second electron mirror as above described.but it is alsopossible to apply any of the heretofore known methods foreffecting this deflection without departing from the scope of myinvention.

What is claimed is:

1. A cathode ray tube including an evacuated vessel, an electron gun foremitting a cathode ray, a fluorescent screen at one end of said vessel,defleeting means for causing said ray to scan said screen, said,deflecting means including an electron mirror located in thepath of saidcathode I my control means for varying the eflective shape of thereflecting surface of said electron mirror, and means for applying ascanning potential to said control means, whereby said cathode ray scansthe surface or said screen in: accordance with variation in the scanningpotential applied to said control means.

2. A cathode ray tube according to claim 1, in which said electronmirror include electrode means for producing an equi-potential surfacein the path of said cathode. ray to reflect said ray at an angle ontosaid fluorescent scream said mirror including further electrode meansfor changing the shape or said equi-potential surface.

i 3. A cathode ray tube including an evacuated vessel having a throatportion and a flared n n tion, an electron gun in said throat portionfor producing a cathode ray, a fluorescent screen at the end or saidflared portion, deflecting means for causing said my to scan saidscreen, said deflecting means including a first virtual electron mirrorin the path of said cathode ray, said electron mirror including meansfor varying the shape or the reflecting surface of said mirror, and asecond virtual electron mirror in the range of said cathode ray forcontinually reproducing said ray on said fluorescent screen alongparallel lines perpendicular to those caused by said first-mentionedelectron mirror, and means for applying scanning potentials 'to saidshape varying means and said second virtual mirror, whereby said cathoderay scans said fluorescent screen along perpendicular coordinates.

